Frequency domain equalization for single-carrier broadband wireless systems
TL;DR: This article surveys frequency domain equalization (FDE) applied to single-carrier (SC) modulation solutions and discusses similarities and differences of SC and OFDM systems and coexistence possibilities, and presents examples of SC-FDE performance capabilities.
Abstract: Broadband wireless access systems deployed in residential and business environments are likely to face hostile radio propagation environments, with multipath delay spread extending over tens or hundreds of bit intervals. Orthogonal frequency-division multiplex (OFDM) is a recognized multicarrier solution to combat the effects of such multipath conditions. This article surveys frequency domain equalization (FDE) applied to single-carrier (SC) modulation solutions. SC radio modems with frequency domain equalization have similar performance, efficiency, and low signal processing complexity advantages as OFDM, and in addition are less sensitive than OFDM to RF impairments such as power amplifier nonlinearities. We discuss similarities and differences of SC and OFDM systems and coexistence possibilities, and present examples of SC-FDE performance capabilities.
Citations
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27 May 2005
TL;DR: The proposed multistage ALSFE significantly outperforms the previous RLS based single-stage adaptive FDE without channel estimation, at comparable complexity, and approaches the performance of LSFE with perfect channel state information (CSI), and has a fast convergence speed.
Abstract: We propose an adaptive layered space-frequency equalization (ALSFE) structure to combat multiple-input multiple-output (MIMO) time-varying frequency selective channels; at each stage of detection, a group of selected data streams are detected, and are then cancelled from the received signals. Two types of adaptive channel estimation approaches are employed for ALSFE, assuming respectively uncorrelated and correlated frequency bins. Noise power estimation is also exploited, which is based on the maximum likelihood (ML) criterion. It is shown that our proposed multistage ALSFE significantly outperforms the previous RLS based single-stage adaptive FDE without channel estimation, at comparable complexity. In particular, ALSFE based on the least-mean-square structured channel estimation (LMS-SCE) approaches the performance of LSFE with perfect channel state information (CSI), and has a fast convergence speed.
2 citations
01 May 2015
TL;DR: This chapter describes the diversity transmission system, multi‐input multi‐output (MIMO) systems, adaptive automatic equalizers, error control techniques, trellis modulation, adaptive interference cancellation, and voice coding.
Abstract: This chapter describes the diversity transmission system, multi‐input multi‐output (MIMO) systems, adaptive automatic equalizers, error control techniques, trellis modulation, adaptive interference cancellation, and voice coding. It discusses the MIMO systems as diversity systems and space‐division multiplexing (SDM) transmission placing emphasis on explanation of their principles. The chapter gives a short introductory description of automatic equalizers and applications to mobile radio channels. To cope with errors in digital transmission, it discusses two countermeasures, namely, error correction and retransmission. Trellis‐coded modulation is a combined coding and modulation technique: coding and modulation are integrated to achieve better error rate performance without compromising bandwidth. Interference cancellation must be adaptive since both the interfering signal and the desired signal are time varying in mobile radio communications. The most straightforward system for voice coding is the usual analog‐to‐digital conversion at periodic sampling instants.
2 citations
01 Nov 2014
TL;DR: A low-complexity Adaptive Frequency Domain Decision Feedback Equalizer for Single-Carrier Frequency Division Multiple Access (SC-FDMA) systems and shows that the RLS-based AFD-DFE not only enjoys a significant reduction in computational complexity when compared to the frequency-domain non-adaptive channel-estimate-based MMSE-DFe but its performance is also better than that of the practical MMSE DFE and close to the ideal MMSEDFE.
Abstract: The decision feedback equalizer is well known to outperform a linear equalizer in highly frequency-selective fading channels. In this paper, we develop a low-complexity Adaptive Frequency Domain Decision Feedback Equalizer (AFD-DFE) for Single-Carrier Frequency Division Multiple Access (SC-FDMA) systems. Both the feedforward and feedback filters operate in the frequency-domain and are adapted using the block Recursive Least Squares (RLS) algorithm. Since this DFE design operation is performed entirely in the frequency-domain, the complexity of the block RLS algorithm can be reduced substantially when compared to its time-domain counterpart by exploiting matrix structure in the frequency-domain. We also show that the RLS-based AFD-DFE not only enjoys a significant reduction in computational complexity when compared to the frequency-domain non-adaptive channel-estimate-based MMSE-DFE but its performance is also better than that of the practical MMSE DFE (with decision errors) and close to the ideal MMSE DFE (with correct decisions).
2 citations
Cites background from "Frequency domain equalization for s..."
...In [3], [4], [5], [6], a hybrid DFE, where the feedforward filter is implemented in the frequency-domain while the feedback filter is realized in the time-domain, is designed for SingleCarrier Frequency-Domain Equalization (SC-FDE) systems....
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TL;DR: A new signal detection scheme is proposed, which combines FDE with MIMO signal detection, such as MMSE detection and Vertical-Bell Laboratories layered space-time architecture (V-BLAST) detection (the authors call this frequency-domain block signal detection), which is evaluated by computer simulation.
Abstract: One-tap frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can significantly improve the bit error rate (BER) performance of single-carrier (SC) transmission in a frequency-selective fading channel. However, a big performance gap from the theoretical lower bound still exists due to the presence of residual inter-symbol interference (ISI) after MMSE-FDE. In this paper, we point out that the frequency-domain received SC signal can be expressed using the matrix representation similar to the multiple-input multiple-output (MIMO) multiplexing and therefore, signal detection schemes developed for MIMO multiplexing, other than simple one-tap MMSE-FDE, can be applied to SC transmission. Then, for the reception of SC signals, we propose a new signal detection scheme, which combines FDE with MIMO signal detection, such as MMSE detection and Vertical-Bell Laboratories layered space-time architecture (V-BLAST) detection (we call this frequency-domain block signal detection). The achievable average BER performance using the proposed frequency-domain block signal detection is evaluated by computer simulation.
2 citations
Cites methods from "Frequency domain equalization for s..."
...…point out that the frequency-domain received SC signal can be expressed using the matrix representation similar to the multiple-input multipleoutput (MIMO) multiplexing and therefore, signal detection schemes developed for MIMO multiplexing, other than simple one-tap MMSE-FDE, can be applied to SC…...
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19 May 2008
TL;DR: Same channel estimation algorithms for OFDM can be applied to the proposed single carrier transmission system due to the similar orthogonal multiplexing of pilot and data symbols in frequency domain.
Abstract: A transmission scheme of orthogonally multiplexing pilots in frequency domain with single carrier data signal is proposed in this paper. In this scheme, information-bearing data symbols are modulated in time domain using a simple precode linear transformation, and multiplexed with pilot symbols in frequency domain. The proposed single carrier transmitter has lower complexity and the transmitted signal has lower peak to average power ratio (PAPR) than that of OFDM. In addition, same channel estimation algorithms for OFDM can be applied to the proposed single carrier transmission system due to the similar orthogonal multiplexing of pilot and data symbols in frequency domain. Equalizers based on MMSE and zero-forcing criteria are also presented. Receiver performance is analyzed and compared with OFDM using numerical examples.
2 citations
Cites background from "Frequency domain equalization for s..."
...Pilot symbol blocks are often periodically inserted in the single carrier modulated signal [1] by time-division multiplexing (TDM) pilot and information symbols....
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...In order to mitigate the inter symbol interference from multi path fading channels, time domain equalizers or frequency domain equalizers (see [1] and the references therein) can be applied at the receiver....
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...For bursty data traffics, which is typical for uplink transmission, a prefix and a postfix are added in order to remove the inter block interference from the adjacent data and pilot blocks [1]....
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References
More filters
Book•
01 Jan 1986
TL;DR: In this paper, the authors propose a recursive least square adaptive filter (RLF) based on the Kalman filter, which is used as the unifying base for RLS Filters.
Abstract: Background and Overview. 1. Stochastic Processes and Models. 2. Wiener Filters. 3. Linear Prediction. 4. Method of Steepest Descent. 5. Least-Mean-Square Adaptive Filters. 6. Normalized Least-Mean-Square Adaptive Filters. 7. Transform-Domain and Sub-Band Adaptive Filters. 8. Method of Least Squares. 9. Recursive Least-Square Adaptive Filters. 10. Kalman Filters as the Unifying Bases for RLS Filters. 11. Square-Root Adaptive Filters. 12. Order-Recursive Adaptive Filters. 13. Finite-Precision Effects. 14. Tracking of Time-Varying Systems. 15. Adaptive Filters Using Infinite-Duration Impulse Response Structures. 16. Blind Deconvolution. 17. Back-Propagation Learning. Epilogue. Appendix A. Complex Variables. Appendix B. Differentiation with Respect to a Vector. Appendix C. Method of Lagrange Multipliers. Appendix D. Estimation Theory. Appendix E. Eigenanalysis. Appendix F. Rotations and Reflections. Appendix G. Complex Wishart Distribution. Glossary. Abbreviations. Principal Symbols. Bibliography. Index.
16,062 citations
"Frequency domain equalization for s..." refers methods in this paper
...Adaptation can be done with LMS (least mean square), RLS, or least squares minimization (LS) techniques, analogous to adaptation of time domain equalizers [Hay96], [Cla98]....
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...Overlap-save or overlap-add signal processing techniques could also be used to avoid the extra overhead of the cyclic prefix [Fer85], [Hay96]....
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TL;DR: The analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel using the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel is discussed.
Abstract: This paper discusses the analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel. This system uses the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel. When this technique is used with pilot-based correction, the effects of flat Rayleigh fading can be reduced significantly. An improvement in signal-to-interference ratio of 6 dB can be obtained over the bursty Rayleigh channel. In addition, with each subchannel signaling at a low rate, this technique can provide added protection against delay spread. To enhance the behavior of the technique in a heavily frequency-selective environment, interpolated pilots are used. A frequency offset reference scheme is employed for the pilots to improve protection against cochannel interference.
2,627 citations
"Frequency domain equalization for s..." refers background in this paper
...OFDM transmits multiple modulated subcarriers in parallel [ 1 ]....
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...Several variations of orthogonal frequency-division multiplexing (OFDM) have been proposed as effective anti-multipath techniques, primarily because of the favorable trade-off they offer between performance in severe multipath and signal processing complexity [ 1 ]....
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TL;DR: In this contribution the transmission of M-PSK and M-QAM modulated orthogonal frequency division multiplexed (OFDM) signals over an additive white Gaussian noise (AWGN) channel is considered and the degradation of the bit error rate is evaluated.
Abstract: In this contribution the transmission of M-PSK and M-QAM modulated orthogonal frequency division multiplexed (OFDM) signals over an additive white Gaussian noise (AWGN) channel is considered. The degradation of the bit error rate (BER), caused by the presence of carrier frequency offset and carrier phase noise is analytically evaluated. It is shown that for a given BER degradation, the values of the frequency offset and the linewidth of the carrier generator that are allowed for OFDM are orders of magnitude smaller than for single carrier systems carrying the same bit rate. >
1,816 citations
TL;DR: This correspondence describes the construction of complex codes of the form exp i \alpha_k whose discrete circular autocorrelations are zero for all nonzero lags.
Abstract: This correspondence describes the construction of complex codes of the form exp i \alpha_k whose discrete circular autocorrelations are zero for all nonzero lags. There is no restriction on code lengths.
1,624 citations